OBSERVATION AND RESULTS
DISCUSSION
A total of 635 patients, from the different units of the Department of Surgery, operated in the main theatre of the Nnamdi Azikiwe University Teaching Hospital, Nnewi from July 2004 to June 2005 were studied. There were 402 (63.3%) males and 233 (36.7%) female patients with a male/female ratio of 3:2. When the paediatric age group was excluded on account of the high number of male circumcision performed in this age group, the sex distribution approximated 1:1 (232 (54.6%) males and 193 (45.4%) females). The peak age range was 21-30 years.
The mean age of the patients was 36±11.4 years. The youngest patient was a day old while the oldest was 81 years. A bar chart of ages of patients studied is shown in Figure 1.
A total of 712 surgical wounds were observed in 635 patients. 593 patients had a single operation wound while 37 patients had 2 surgical wounds and 5 patients had more than 2 surgical wounds. Majority of the wounds are classified as clean (51.69%) followed by clean contaminated (33.57%) (Table 3). 10.25% of the wounds were contaminated and 4.49% were dirty wounds.
Figure 1: Age Distribution No of pts
TABLE 3: WOUND CLASSIFICATIONS
TYPE OF OPERATION NUMBER OF WOUNDS PER CENT (%)
Clean 369 51.69%
Clean contaminated 239 33.57%
Contaminated 73 10.25%
Dirty 32 4.49%
Total 712 100%
104
63 61 125
88
53 46 69
26
0 20 40 60 80 100 120 140
Age group
<1mth
<10yrs 11-20yrs 21-30yrs 31-40yrs 41-50yrs 51-60yrs 61-70yrs
>70yrs
Linear (<1mth)
Forty nine percent of the procedures were classified as minor while 20.22% were intermediate (Table 4). The procedures were classified depending on the duration of the procedure and the expertise required. (see Appendix 4)
Table 4: Classification of procedures
TYPE OF PROCEDURE NUMBER OF WOUNDS PERCENTAGE
Minor 353 49.58%
Intermediate 143 20.22%
Major 216 30.20%
Total 712 100%
Table 5. Classification of procedure according to sex
MAJOR INTERMEDIATE MINOR TOTAL Male 95 (22.04%) 86 (19.96%) 250 (58%) 431 (100%) Female 121 (43.06%) 57 (20.29%) 103 (36.65%) 281 (100%) Total 216 (30.34%) 143 (20.08%) 353 (49.58%) 712 (100%)
It was observed that majority of the males underwent minor procedures when compared with the females (p=0.049).
Table 6. Classification of procedure according to sex and age
MALE FEMALE
ADULT PAEDIATRICS ADULT PAEDIATRICS
Major 76 19 100 21
Intermediate 61 25 37 20
Minor 117 133 94 9
Total 254 177 231 50
Majority of the infections observed were superficial incisional which accounted for 81.56% of the cases. 10 patients (13.16%) had deep incisional and 4 patients (5.26%) had organ and space surgical site infections. Thirty-eight infected patients were males accounting for 52.8% of the infected patients while the remaining 34 patients were females (47.2%).
Seventy six out of the 712 wounds studied became infected, yielding an infection rate of 10.56% (Table 5). The rate of infection of clean wounds was 4.89% but when pus is encountered at operation (Dirty), the rate of infection was 37.5%
(P=0.01). The greater the degree of contamination at operation the higher the risk of wound infection.
Table 7: Analysis of infection rate related to wound types p=0.01
WOUND CLASS NUMBER OF
WOUNDS
NUMBER INFECTED
PERCENTAGE
Clean 368 16 4. 89%
Clean contaminated 239 28 10.88%
Contaminated 73 20 27.4%
Dirty 32 12 37.5%
Total 712 76 10.56%
Bacteria growth was observed in 65 surgical wounds of the 76 surgical wound studied. Mixed flora was obtained in 3 patients and the rest were pure colonies.
Anaerobic and aerobic cultures were done for 35 patients out of the 76 patients while the remaining 41 patients had only aerobic cultures. In the 35 patients with anaerobic and aerobic cultures 1 patient had a mixed organism, and no growth was observed in 5 patients.
Table 8: Microbiology of all infected wounds
TYPE OF ORGANISM NUMBER PERCENTAGE
Coliform organisms Pseudomonas E coli
Klebsiella Proteus
Non characterized 44
13
7
3
1
20
54.32%
16.05%
8.64%
4.65%
3.70%
24.69%
Staphylococcus aureus 17 20.99%
Anaerobes 6 7.40%
No growth 14 17.28%
Total 81 100%
Table 8 shows the pattern of the bacterial isolates with coliform organisms accounting for 54.32% of all isolates. This was followed by Staphylococcus aureus (18.6%). The commonest of the Coliform organisms was Pseudomonas accounting for 16.05%. Other species include Escherichia coli, Klebsiella and Proteus which accounted for 8.64%, 4.65% and 3.7% respectively. The uncharacterized Coliform
organisms accounted for 24.69%. No growth was observed in 14 patients constituting 17.28% of the samples.
Anaerobic culture was positive in 6 patients and yielded a variety of organism. The most commonly encountered anaerobic organism was Anaerobic Streptococcus and it accounted for 50% of all the strains. This was followed by Clostridium welchii in 2 patients and Anaerobic Neisseria in 1 patient.
In all the cases of infection where Staphylococcus aureus was isolated, it was pure culture. It was only isolated in the superficial incisional wound infections.
Staphylococcus aureus was commonly isolated in the minimally contaminated wounds at operation. Coliforms was commonly isolated in urological operations where the urine culture is also positive with the same organisms.
The mean hospital stay in all patients was 15.46 days (SD 14.02). The mean for infected patients was 40.58 days (SD 28.08) while that for the non-infected ones was 8.76 days (SD 7.2) p=0.04. 62 patients (81.57%) were diagnosed while still on admission while 14 patients (18.42%) were diagnosed after discharge. Twelve patients died during the course of the study. Seven were clinically infected while five were not. Wound infection was diagnosed in 46 patients (60.5%) during the first week while 21 patients (27.6%) were diagnosed during the second week. The
rest (11.9%) had their wound infection diagnosed after the third week of operation.
Surgical site infection was detected at 10.7 5.92 days.
Table 9: Duration/type of surgery and wound infection DURATION OF
SURGERY
NO OF WOUNDS
NO OF WOUNDS INFECTED
PERCENT P VALUE
<2 hours 446 19 4.26
> 2 hours 266 57 21.43
Total 712 76 10.56 0.01
The mean duration of all operations was 125.65 minutes (SD ± 59.42). The minimum duration was 12 minutes while the longest lasting operation was 320 minutes. The mean duration of those who developed wound infection was 168. 46 minutes (SD ± 60.22) Nineteen (4.26%) of 446 patients whose operation lasted less than two hours developed ond infection, while 57 (21.43%) of 266 patients whose operations lasted for two hours or more developed wound infection (p=0.01).
There was a general trend of increasing infection rates with increasing indices in the ASA, NNIS and SENIC scores and the differences in the infection rates are statistically significant for all the predictive indices. P values ranged from 0.042 in the ASA group to 0.006 in the SENIC index. (Tables 10 – 12).
Table 10: ASA score and wound infection ASA SCORE NO OF
WOUNDS
NO OF WOUNDS INFECTED
PERCENT P VALUE
I-II 618 30 4.85
III-V 94 46 48.94
Total 712 76 10.62 0.042
Table 11: NNIS score and wound infection NNIS
SCORE
WOUNDS INFECTED
WOUNDS NOT INFECTED
TOTAL WOUNDS
% INFECTED
P VALUE
0 4 118 122 3.28
1 29 379 408 7.11
2 30 116 146 20.58
3 13 23 36 36.11 0.025
Table 12. SENIC Score and wound infection SENIC
SCORE
WOUNDS INFECTED
WOUNDS NOT INFECTED
TOTAL WOUNDS
% INFECTED
P VALUE
1 5 102 107 4.67
2 33 425 458 7.20
3 24 78 102 26.47
4 14 311 45 31.1 0.006
Table 13: Emergency compared with Elective Surgery NO OF
WOUNDS
NO OF PTS WOUNDS
PERCENT P VALUE
Emergency 76 32 42.11
Elective 636 44 6.92
Total 712 76 10.62 0.05
76 patients (10.7%) had emergency surgery with an infection rate of 42.11%.
Majority of these procedures were suprapubic cystostomy for bladder outlet
obstruction. Elective operations had an infection rate of 6.92% (p=0.05) as shown in Table 13.
Table 14: Infected wounds according to Surgical Specialty TYPE OF
SURGERY
TOTAL NO. OF WOUNDS
INFECTED WOUNDS
PERCENTAGE
Orthopaedic 86 18 20.93%
Urology 135 27 20%
Laparotomy 58 8 13.79%
Breast 74 8 10.81%
Appendicectomy 28 2 7.14%
Plastic 24 1 4.17%
Paed Surg 198 5 2.53%
Others 109 7 6.42%
Total 712 76 10.56%
Table 14 shows the wound infection rates in the different categories of operations.
The commonest surgery with most infections was Orthopaedic surgery follwed bu Urology. Most Orthopaedic surgery wounds were contaminated while Urology could also be explained from the fact that most of the patients were catheterized and most of them have urinary tract infection. 25 patients (48%) out of 52 patients
with UTI/Urinary catheter had infection. (p=0.035) 10 patients (41.7%) out of 24 patients had 1 or more courses of chemotherapy had infection (p=0.023)
Table 15: Infections in major surgeries compared to the calibre of the Principal Surgeon
SURGEON NO OF
WOUNDS
INFECTED WOUNDS
% P VALUE
Consultant 152 28 18.42
Senior resident 54 9 16.7
Total 216 37 17.13 0.042
Most of the surgeries performed by the consultants had high indices for wound infection using the ASA, SENIC and NNIS indices for wound infection when compared with those carried out by the residents (Table 15).